It is desirable to monitor the state of an actuatable switch device in various types of electrical devices. In an automobile, for example, numerous vehicle accessories are responsive to the operative position of a vehicle ignition switch. Typically, a direct connection from the vehicle ignition switch to a monitoring circuit is used to detect whether the vehicle ignition is ON. This conventional approach is illustrated, for example, in U.S. Pat. No. 2,698,893, U.S. Pat. No. 4,926,025, and U.S. Pat. No. 5,229,579. Similarly, U.S. Pat. No. 4,903,011 discloses a lamp drive circuit having a main drive circuit and a separate back-up drive circuit for energizing a lamp through a vehicle ignition switch.